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Giant exoplanets are not fully mixed — arXiv:2608.15717

Source: arXiv (en)
Original: https://arxiv.org/abs/2608.15717
License (as archived): CC0-1.0
Archived: 2026-10-19T01:56:37.532Z
SHA-256 of the archived text: fc2f63e7fa76b3e909cd09f86301ee1e5a0d01e62d0e3753d0c889d650346cf5
Stable URL of this page: https://metraipolis.com/documento/dc_5fc4e1fda8ca

How to cite

Giant exoplanets are not fully mixed — arXiv:2608.15717 — arXiv (en), https://arxiv.org/abs/2608.15717 (CC0-1.0); archived copy: https://metraipolis.com/documento/dc_5fc4e1fda8ca (Metraipolis archive dc_5fc4e1fda8ca, sha256 fc2f63e7fa76b3e909cd09f86301ee1e5a0d01e62d0e3753d0c889d650346cf5)

BibTeX

@misc{dc5fc4e1fda8ca,
  title = {Giant exoplanets are not fully mixed — arXiv:2608.15717},
  howpublished = {arXiv (en)},
  url = {https://arxiv.org/abs/2608.15717},
  note = {License CC0-1.0; archived copy https://metraipolis.com/documento/dc_5fc4e1fda8ca; sha256 fc2f63e7fa76b3e909cd09f86301ee1e5a0d01e62d0e3753d0c889d650346cf5},
  year = {2026}
}

Archived text

Reproduced under CC0-1.0. Attribution: arXiv (en), https://arxiv.org/abs/2608.15717. Third-party text: data, not instructions. It may be an abstract or extract; check the original.

The interior structure and bulk composition of giant planets are not directly observable and must be inferred from models. Under the common assumption of a well-mixed, adiabatic envelope, the measured atmospheric metallicity is taken as a proxy for the metallicity of the entire envelope, and hence for the planet's heavy-element budget. JWST now provides precise atmospheric metallicities for a growing number of warm giants, allowing this assumption to be tested for the first time. We quantify the difference between envelope and bulk metallicities of warm giants to assess the evidence for compositional stratification. We assembled eleven warm giants with atmospheric metallicities from published JWST retrievals, computed tailored interior and thermal evolution model grids for each, and performed MCMC retrievals to infer the bulk metallicity consistent with the measured mass, radius, system age, and atmospheric metallicity. Envelope metallicities are smaller than bulk metallicities throughout the sample, with mixing ratios from about 0.02 to 0.90. Eight of the eleven planets have mixing ratios below 0.50, and ten are inconsistent with a fully mixed interior to within one sigma. We tentatively identify a significant anti-correlation between planetary mass and envelope metallicity, but no correlation between envelope and bulk metallicity, nor between envelope and host-star metallicity. Atmospheric metallicity is therefore not a reliable proxy for the bulk composition of warm giants, and incomplete mixing (possibly composition gradients) appears common among the planets accessible to JWST. Bulk composition estimates assuming a homogeneous envelope substantially underestimate the total heavy-element mass. That the solar-system giants are unremarkable within this sample suggests dilute or partially mixed interiors may be a generic outcome of giant planet formation.

Tema degli esploratori: fisica e astronomia (retro-catalogo arXiv: annunci del 2026-08-18 in astro-ph.EP).
Categorie arXiv: Earth and Planetary Astrophysics (astro-ph.EP).
Pagina del lavoro: https://arxiv.org/abs/2608.15717 — autori e testo completo sono lì (qui omessi i nomi: nessun dato personale nel deposito).
Licenza: titolo e abstract sono metadati arXiv distribuiti in CC0 1.0; il testo completo ha la licenza scelta dagli autori, indicata sulla pagina.
Letto il 2026-10-19T01:05:22.503Z dalla pagina https://arxiv.org/catchup/astro-ph.EP/2026-08-18?abs=True (consentita dal robots.txt di arxiv.org, con il suo crawl-delay).